With the development of science and technology, CRT display devices that are quite heavy have been substituted by flat panel display devices which are increasingly merging into people's daily lives. The liquid crystal display (LCD) device is a kind of flat panel display device having a liquid crystal (LC) panel as its major component. The LC panel substantially comprises a color filter (CF) substrate and an array substrate, and liquid crystals filling there-between. An electrode for generating an electric field is also disposed in either the array substrate or the CF substrate. The structure and configuration of the electrode can determine the deflection of the liquid crystals, thus influence the display of the LC panel. The LC panel is provided with a plurality of pixel points (each generally includes three sub-pixels, i.e., R, G, and B) each controlled by a thin film transistor (TFT) manufactured in the array substrate during the imaging, so as to achieve active driving and image displaying. The TFT, as a controlling switch, is the key point for achieving the display function of a LCD display, and has the direct bearing on the development direction of high-performance flat panel display devices.
The ADvanced Super Dimension Switch (ADS, also referred to ADSDS) technology emerges as required by the development of LCD technique and the demands for high brightness, high contrast ratio and low energy consumption. The ADS-based array substrate usually comprises two layers of electrodes located at a same side of the LC cell, one of which is a slot electrode layer and the other is a plate electrode layer. By forming a multi-dimensional electric field consisted of an electric field generated between edge of slit electrode and the plate electrode layer and an electric field generated between slit electrodes, all the LC molecules located in the LC cell are deflected, so that the working efficiency of the liquid crystals is improved and the viewing angle is broadened. The ADS technique can increase the aperture ratio of pixels, thereby raising the brightness, reducing the energy consumption, as well as improving the quality level of a LCD panel and the image quality of TFT-LCD products.
Generally, for a ADS-based array substrate, a plate-like common electrode is located in a lower layer while a slit-like pixel electrode is located in an upper layer in a sub-pixel unit. For a high aperture ADS (H-ADS)-based array substrate, a plate-like pixel electrode, which is connected with a drain electrode of TFT, is located in a lower layer while a slit-like common electrode is located in an upper layer, in a sub-pixel unit. For a H-ADS-based array substrate, since a pixel electrode is covered by a passivation layer (PVX) and a common electrode which are located on the pixel electrode, a test probe cannot access the pixel electrode or the drain electrode when an electrical characteristic test is conducted on a TFT (such as a test on switching current, threshold voltage and electron mobility of the TFT) in the sub-pixel unit, after the array substrate is made; as a result, it is impossible to test the characteristics of the TFT, which further leads to inconvenience in monitoring the electrical characteristics of the TFT. Therefore, it requires a prompt solution in the industry to improve the convenience for measuring a pixel electrode in an array substrate and to improve the product quality of the array substrate.